The system of systemic veins (capacitance vessels) constitutes a reservoir which makes blood available to the heart. The pressure within the reservoir is controlled to a large degree by neural regulation of venous tone. This pressure is an important determinant of cardiac filling and under steady conditions an equilibrium exists between filling pressure and cardiac output. The relationship is such a wide range of body activity. Maintenance of this balance between filling pressure and output in the face of variable demands on the circulation implies a high level of integration between the control of venomotor tone and the control of myocardial function and heart rate. There have been many studies on the neural regulation of myocardial function and heart rate and information is accumulating about venous mechanisms which influence filling pressure. Little, however, is known about the interplay of venous and cardiac responses to afferent stimuli at the functional level and even less is known about neural integration of these responses. The objectives of the proposed research are to learn more about the functional interplay of venous and cardiac responses to a number of afferent stimuli; to study mechanisms of integration of venous and cardiac responses to these stimuli; to compare capacitance vessels of the limbs, mesentery and spleen with respect to their responses to various vasoactive agents and to stimuli mediated by way of reflex pathways; to examine the function of the capacitance vessels in experimental shock; and to study the role of the veins in the pathophysiology of a number of clinical disorders.